The mechanisms of electron transfer reactions involving soft center such as sulfur is intriguing since there are a multitude of compounds containing biologically important sulfhydryl and disulfide groups. One of such types is the imidazole-2-thione which is used in the thyroid peroxidase-catalyzed iodination of thyroglobulin. Another example is the use of 2-thiouracil derivatives in the treatment of hyperthyroidism. Since thiyl free radicals might be implicated in the above in vivo biochemical processes, it becomes apparent that the nature and the mechanisms of the oxidation reactions with various oxidizing reagents must be understood to permit a better understanding of the role of sulhydryl and disulfide in the efficacy of the medicine. In the present proposal, we plan to investigate the kinetics and mechanisms of the above redox processes with single and multi-electron transfer transition metal complexes as oxidants and compare the different pathways the reactions might have taken when changes in coordination and free energy are imposed. All the transition metals will be of unusual hyper oxidation states with substitution inert property essential for the control of the redox chemistry. Student participants will be given the opportunity to synthesize, characterize, and study the kinetics of reactions of these complexes. They will be taught the procedure to prepare inorganic complexes and how to use various instruments. They are expected to participate fully in group meetings and in conference presentations.